A systematic selection and evaluation of helium-cooled blanket concepts has been performed as part of the Blanket Comparison and Selection Study (BCSS). Helium-cooled Li2O, lithium, LiAlO2/Be, and Flibe/Be blanket concepts were selected for detailed design and evaluation. These concepts are applicable to both tokamak and tandem mirror reactors (TMRs). The design and analysis of Li2O, lithium, and LiAlO2/Be blanket concepts are presented. Previous blanket designs were studied and the pressurized lobe configuration was selected for the helium-cooled BCSS designs. Fifty-four different combinations of structural, breeder, and neutron multiplier materials were considered and four helium-cooled blanket concepts were selected for detailed design and evaluation. Mechanical, thermal, and neutronic designs were developed, and tritium control methods were specified. In the final BCSS evaluation, the Li2O blanket design ranked second for tokamaks and third for TMRs. The lithium blanket design ranked third for tokamaks and fourth for TMRs. To help guide future research and development, the critical issues associated with each of the helium-cooled designs were identified and necessary experimental data highlighted. These data include irradiation behavior of the blanket materials, compatibility between the structure and liquid-metal breeder materials, and the behavior of tritium in a helium-cooled blanket environment. The designs offer favorable performance, design simplicity, and attractive safety features for fusion reactors. Design improvements were identified that could allow still better performance of the helium-cooled blanket designs.